The present invention relates to polyamide resin compositions having excellent mechanical properties and moldability and showing excellent weld strength. The resin compositions are used as materials for automobiles or electrical or electronic parts.
Crystalline polyamide resins have widely been used as industrial materials owing to their high strength and rigidity. However, reinforced polyamides using only crystalline polyamides as polyamide show insufficient weld strength due to their crystallinity when subjected to welding which has become often used in recent years in production of resinous parts. Thus, they can not be used for parts requiring a high weld strength. In cases when polyamides composed of non-crystalline polyamides alone are used, there can be obtained enough vibration weld strength, but moldability, in particular flowability, is so poor that injection weld strength is low, which has limited the use of them.
With the recent increase in number of parts formed by using welding technique, various investigations have been made as to techniques for improving weld strength of crystalline polyamides. JP-A-9-176484 (The term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and JP-A-10-219106 propose a technique of using copper iodide and potassium iodide to improve welding properties of nylon. However, this technique involves the problem that, since the amounts of actually used potassium iodide and copper iodide are so large, there result decreased mechanical strength and generation of a decomposition gas upon molding. JP-A-8-337718 proposes a technique of using a crystalline copolymer nylon. In cases of using the copolymer nylon, welding properties are markedly improved, but there result decreased mechanical strength and decreased rigidity and decreased durability including heat resistance, which limits the use of the copolymer nylon.
Compositions analogous to the composition of the present invention have long been known, and are disclosed in JP-A-58-53949 and JP-A-58-53950. These inventions, however, are techniques for improving metal halide resistance, hot water resistance or warping resistance of aliphatic nylons, and hence a larger amount of non-crystalline nylon is required to be added in comparison with the present invention. It has not been known at all to obtain the effect of improving welding properties within the composition range of the present invention.
The present invention provides a polyamide resin composition which shows excellent flowability upon molding, high cycling properties, and high weld strength when subjected to various welding methods, thus solving the above-described problems.
As a result of intensive investigations to solve the problems, the inventors of the present invention have found that the problems can be solved by adding a non-crystalline, partially aromatic copolymerized polyamide resin containing at least two aromatic monomer components in an extremely small amount to a crystalline polyamide resin, thus having completed the present invention based on the finding.
That is, the present invention relates to a polyamide resin molding composition, which shows excellent weld strength and which comprises:
(A) 96 to 99.9% by weight of a crystalline polyamide resin and;
(B) 0.1 to 4% by weight of a non-crystalline, partially aromatic, copolymerized polyamide resin containing at least two aromatic monomer components, with the total content of the crystalline polyamide and the non-crystalline, partially aromatic, copolymerized polyamide resin being 100% by weight.
Further, the present invention relates to a polyamide resin molding composition, which further comprises (C) 5 to 200 parts by weight of an inorganic filler per 100 parts by weight of the above-described polyamide resin molding composition.